How to add a Google Gemini chatbot to WordPress, and what it really costs

Why Gemini for a website chatbot

• Low cost per answer. Flash and Flash-Lite models cost a fraction of a cent per question, so a busy site pays a few dollars a month.
• Fast replies. Flash models are built for quick responses, which matters in a chat window.
• Embeddings from the same provider. Gemini’s embedding model turns your pages into an index the chatbot searches, with one key and one bill.
• Many languages. It answers visitors in their own language from your English content.

Other providers work well too. What matters more than the model is how the chatbot uses it: whether it answers only from your content, and what it does when it can’t.

What you need

• A WordPress site where you can install plugins
• A chatbot plugin that supports Google Gemini and calls it from your server, not from the visitor’s browser
• A Google account for Google AI Studio
• A payment card for billing (at least $5 of prepaid credit)
• About 15 minutes

Step by step

1. Create an API key

   Go to aistudio.google.com/api-keys and click Create API key. Choose a project, or let AI Studio create one, then copy the key. Since 28 May 2026 new keys are “auth keys”, restricted to the Gemini API by default.

2. Set up billing

   Next to your project, click Set up billing, choose your country and add a payment method. New accounts prepay: add at least $5 of credit and turn on auto-reload.

3. Paste the key into your plugin

   In HolaReply this is Settings → AI connection, as the AI key docs show. The key is encrypted with your site’s own keys, never shown again and never sent to the browser.

4. Choose what it reads

   Tick your pages, posts and WooCommerce products. The plugin creates embeddings of your content, which costs cents, once.

5. Test it

   Ask a question your site answers, one it doesn’t, and one in another language. Check the answer shows its source and the unanswered one reaches your team.

Google’s own guidance is clear: never put an API key in code that runs in the visitor’s browser. A chatbot plugin should call Gemini from your WordPress server. If a plugin asks you to paste the key into a script tag or a page, choose another plugin.

Which Gemini model to use

For a website chatbot, a Flash model is the right choice: fast, cheap and good at answering from the text it is given. Prices below are Google’s standard paid-tier prices on 25 September 2026, per million tokens.

Output prices include “thinking” tokens. Batch and Flex processing cost less but are not suited to live chat.

Watch out for old models. Google now limits the Gemini 2.5 models to people who have used them before, and tells new projects to use 3.5 Flash-Lite or 3.8 Flash. A plugin hard-wired to a 2.5 model can fail on a new key with a “no longer available to new users” error.

What 1,000 questions really cost

A chatbot question is more than the visitor’s words. The plugin also sends the passages it found on your site and its instructions. A realistic estimate is about 2,500 input tokens and 250 output tokens per answer, plus a tiny embedding call to search your index.

The arithmetic for 3.8 Flash today: 2.5M input tokens × $0.75 + 0.25M output tokens × $3.75 + 0.03M embedding tokens × $0.20 = $2.82. If the model “thinks” before answering, output tokens and cost go up. Indexing a 500-page site once costs roughly $0.10.

Compare that with hosted chatbot services that charge per conversation or per message credit, often $30–150 a month for similar volumes. See our cost comparison.

Free tier or paid: the rules that matter

From Google’s Gemini API Additional Terms of Service and pricing page. Google also says not to send sensitive, confidential or personal information to the free tier.

In short: test on the free tier, go live on paid. For a small business the paid tier usually costs less than a coffee a month, and it removes the data and legal questions.

Make it answer only from your website

On its own, Gemini will answer almost anything from its general knowledge. On a business website that is a risk: it can state a price, a delivery time or a policy you never wrote. A good chatbot plugin gives Gemini only the passages it found on your site, tells it to answer from those or not at all, and shows the source under each answer.

Note that “Grounding with Google Search”, a Gemini feature, is something different: it answers from the web, not from your site, and costs extra after the first 5,000 requests a month. For a business chatbot you want your own content, not the web.

Answers from your own pages, with the source shown; nothing found means the visitor is offered a person.

Privacy

• Use a paid key, so Google doesn’t use your visitors’ questions to improve its products.
• Remove personal details before anything is sent. HolaReply strips names, email addresses, phone numbers and company names from every question first.
• Keep conversations in your own WordPress database, and mention the chatbot and Google as a provider in your privacy policy.
• Google’s terms say Gemini API services are for businesses and not for sites aimed at people under 18.

Gemini chatbot plugins for WordPress

From each plugin’s own WordPress.org or product page. See also our AI Engine comparison.

Common errors and what they mean

“No longer available to new users”

The plugin is asking for a retired model, usually Gemini 2.5. Switch to a current Flash or Flash-Lite model, or update the plugin.

HTTP 402, or every request fails at once

Your prepaid credit has run out, and Google stops all keys on the project. Add credit and turn on auto-reload.

HTTP 429, “resource exhausted”

You have hit a rate limit, usually on the free tier. Turn on billing or wait for the daily reset at midnight Pacific time. HolaReply pauses and carries on by itself, and visitors can still send an enquiry meanwhile.

“API key not valid”

Check you copied the whole key. Google is switching off older “standard” keys during 2026, so if yours is old, create a new one in AI Studio.

Questions people ask

Sources

Checked on 25 September 2026. Prices and features change; tell us in the chat if something here is out of date and we will fix it.

1. Gemini API pricing
2. Gemini API models (including access to 2.5 models)
3. Gemini API rate limits and usage tiers
4. Gemini API Additional Terms of Service
5. Using Gemini API keys (auth keys)
6. Gemini API billing (prepay, 402 errors, credits)
7. AI Engine on WordPress.org
8. WoowBot pricing
9. Sublimity AI Chatbot for Google Gemini on WordPress.org
10. Mates: Gemini Chatbot for WordPress on CodeCanyon

Maqsood R.

Founder of HolaReply. He builds AI assistants that answer only from a business’s own website, and checks every fact in these guides against the products’ own pages.

More by Maqsood R. →